1. Field of the Invention
Generally, the invention relates to a sheet extracting device having a cassette for receiving a stack of sheets, and having a pressing element which bears against a first end face of the stack of sheets and is movable in the pressing direction. More specifically, the invention relates to such a device wherein a drive motor displaces the pressing element so that a second end face of the stack of sheets can be pressed against extracting elements. Furthermore, the invention relates to a sheet extracting device having a measuring device for determining the pressing force of the second end of the stack of sheets against the extracting elements, wherein an output signal of the measuring device controls the drive motor to generate a predetermined pressing force.
2. Description of the Related Art
Cassettes are used in sheet extracting devices, particularly in automatic banknote dispensers. A stack of banknotes located in the cassette is pressed by a pressing element against an end wall of the cassette, which is designed such that the respectively forwardmost banknote is in contact with extracting elements reaching through the end wall. These extracting elements are normally extracting rollers, but may also be extracting fingers or the like.
It is already known to press the stack of banknotes by a spring biased pressing plate against the extracting elements, the pressing plate triggering the control of a pressing slide by means of a displacement sensor. In such a device, it is, difficult to maintain constant pressing force, since the friction of the banknotes in the cassette changes with the number of banknotes in the stack and according to their condition (bends, folds and the like).
In the case of a known sheet extracting device such as that disclosed in German Patent No. DE34 34 780 C2, the stack of banknotes is pressed against the extracting rollers by a pressing plate, which is displaced in the cassette by a drive motor. The pressing force of the extracting rollers against the forwardmost banknote is measured and used for controlling the drive motor.
Although the pair at sheet extracting device operates satisfactorily, it has been difficult to measure the pressing force, which can be carried out at the bearings of the extracting roller shaft if the latter is movably mounted.